U.S. patent application number 15/685609 was filed with the patent office on 2018-05-03 for method of forming topcoat for patterning.
The applicant listed for this patent is Massachusetts Institute of Technology, University of Chicago. Invention is credited to Karen K. Gleason, Do Han Kim, Priya Moni, Paul Franklin Nealey, Hyo Seon Suh.
Application Number | 20180122648 15/685609 |
Document ID | / |
Family ID | 62022531 |
Filed Date | 2018-05-03 |
United States Patent
Application |
20180122648 |
Kind Code |
A1 |
Kim; Do Han ; et
al. |
May 3, 2018 |
Method of Forming Topcoat for Patterning
Abstract
Disclosed is a method for the fabrication of polymeric topcoat
via initiated chemical vapor deposition (iCVD) or photoinitiated
chemical vapor deposition (piCVD) in conjunction with directed
self-assembly (DSA) of block copolymers to generate high resolution
patterns. A topcoat deposited by iCVD or piCVD allows for
conformal, ultra-thin, uniform, pinhole-free coatings. iCVD or
piCVD topcoat enables the use of a diversity of block copolymer
(BCP) materials for DSA and facilitates the direct and seamless
integration of the topcoats for a pattern transfer process.
Inventors: |
Kim; Do Han; (Melrose,
MA) ; Suh; Hyo Seon; (Woodridge, IL) ; Moni;
Priya; (Worcester, MA) ; Gleason; Karen K.;
(Cambridge, MA) ; Nealey; Paul Franklin; (Chicago,
IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Massachusetts Institute of Technology
University of Chicago |
Cambridge
Chicago |
MA
IL |
US
US |
|
|
Family ID: |
62022531 |
Appl. No.: |
15/685609 |
Filed: |
August 24, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62416299 |
Nov 2, 2016 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/31138 20130101;
H01L 21/3086 20130101; H01L 21/31144 20130101; C23C 16/46 20130101;
H01L 21/02271 20130101; H01L 21/3081 20130101; H01L 21/3065
20130101; H01L 21/02118 20130101; G03F 7/0002 20130101; H01L
21/02178 20130101; H01L 21/0228 20130101 |
International
Class: |
H01L 21/308 20060101
H01L021/308; C23C 16/46 20060101 C23C016/46; H01L 21/311 20060101
H01L021/311; H01L 21/3065 20060101 H01L021/3065 |
Goverment Interests
GOVERNMENT SUPPORT
[0002] This invention was made with Government support under Grant
No. CMMI-1344891 awarded by the National Science Foundation. The
Government has certain rights in the invention.
Claims
1. A method of forming a topcoat on a block copolymer film,
comprising the steps of: (a) heating or irradiating an initiator,
thereby producing a gaseous free radical initiator; (b) contacting
the block copolymer film with the gaseous free radical initiator
and a gaseous monomer, thereby forming a cross-linked topcoat.
2. The method of claim 1, wherein the initiator is selected from
the group consisting of a peroxide, an aryl ketone, and an azo
compound.
3. The method of claim 1, wherein the initiator is
triethylamine.
4. The method of claim 1, wherein the initiator is an aryl
ketone.
5. The method of claim 1, wherein the initiator is an azo compound
selected from the group consisting of 4,4'-Azobis(4-cyanovaleric
acid), 4,4'-Azobis(4-cyanovaleric acid),
1,1'-Azobis(cyclohexanecarbonitrile),
2,2'-Azobis(2-methylpropionamidine) dihydrochloride,
2,2'-Azobis(2-methylpropionitrile), and
2,2'-Azobis(2-methylpropionitrile).
6. (canceled)
7. The method of claim 1, wherein the initiator is a peroxide
selected from the group consisting of tert-butyl hydroperoxide,
tert-butyl peracetate, cumene hydroperoxide, dicumyl peroxide,
benzoyl peroxide, tert-amyl peroxide, tert-butyl peroxide, and
tert-butyl peroxybenzoate.
8. (canceled)
9. The method of claim 1, wherein the monomer is at least one of an
acrylate, a siloxane, a silazane, and a vinyl compound.
10. The method of claim 9, wherein the monomer is selected from the
group consisting of methyl methacrylate, butyl acrylate, glycidal
methacrylate, vinyl pyridine, divinylbenzene, stylene,
trivinlytrimethylcyclotrisiloxane,
tetravinyltetramethylcyclotetrasiloxane,
trivinyltrimethylcyclotrisilazane, and
tetravinyltetramethylcyclotetrasilazane.
11. (canceled)
12. The method of claim 1, wherein the block copolymer film is
formed by a method comprising the steps of: (a) providing a
substrate; (b) forming a lithographically defined physical or
chemical pattern on the substrate; and (c) coating the substrate
with a block copolymer.
13. The method of claim 12, wherein the substrate is selected from
the group consisting of silicon wafer, glass slide, quartz,
polyurethane, polyorthoester, polyacrylonitrile, polyphenazine,
teflon, polyamide resin, GORE-TEX.RTM., MARLEX.RTM., expanded
polytetrafluoroethylene (e-PTFE), polyimide (PI), and polypropylene
(PP).
14. The method of claim 12, wherein the substrate is a silicon
wafer.
15. The method of claim 1, wherein the physical or chemical pattern
formed by photolithography or electron-beam lithography.
16-19. (canceled)
20. The method of claim 1, wherein the block copolymer is selected
from the group consisting of poly(styrene-block-methacrylate),
poly(2-vinylpyridine)-block-polystyrene-block-poly(2-vinylpyridine),
poly(styrene-block-ethylene oxide), and
poly(styrene-block-dimethylsiloxane).
21-23. (canceled)
24. The method of claim 1, wherein forming the topcoat comprises
initiated chemical vapor deposition (iCVD) or phoroinitiated
chemical vapor deposition (piCVD) of the topcoat in a deposition
chamber.
25. The method of claim 1, wherein the topcoat is pinhole-free.
26-27. (canceled)
28. The method of claim 1, wherein the thickness of the topcoat is
less than about 10 nm.
29. An article, comprising a substrate, and a coating on the
substrate, wherein the coating comprises a block copolymer film and
a topcoat on the block copolymer, wherein the topcoat is deposited
by iCVD or piCVD.
30-34. (canceled)
35. A method of forming a pattern on an article of claim 29,
comprising the steps of: (a) coating the article with a resist; (b)
forming a resist pattern using lithography to form a mask; (c)
removing the topcoat from the masked article by a first reactive
ion etching; (d) removing the remaining polymer of the article by a
second reactive ion etching; and (e) etching the substrate by a
third reactive ion etching.
36-51. (canceled)
52. A memory circuit, comprising a pattern obtained by a method of
claim 35.
53. A microprocessor, comprising a pattern obtained by a method of
claim 35.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of priority to U.S.
Provisional Patent Application Ser. No. 62/416,299, filed Nov. 2,
2016.
BACKGROUND
[0003] Directed self-assembly is a promising strategy for
high-volume cost-effective manufacturing at the nanoscale. Over the
past decades, manufacturing techniques have been developed with
such remarkable efficiency that it is now possible to engineer
complex systems of heterogeneous materials at the scale of a few
tens of nanometers to support the every growing market for
semiconductors, which exceeded $300 billion in 2010. Further
evolution of these techniques, however, is faced with difficult
challenges not only in feasibility of implementation at scales of
10 nm and below, but also in prohibitively high capital equipment
costs. Materials that self-assemble, on the other hand,
spontaneously form nanostructures down to length scales at the
molecular scale. The micrometer areas or volumes over which the
materials self-assemble with adequate perfection in structure is
incommensurate with the macroscopic dimensions of working devices
and systems of devices of industrial relevance. Directed
Self-Assembly (DSA) refers to the integration of self-assembling
materials with traditional manufacturing processes. The key concept
of DSA is to take advantage of the self-assembling properties of
materials to reach nanoscale dimensions and at the same time meet
the constraints of manufacturing. Put another way, DSA enables
current manufacturing process capabilities to be enhanced and
augmented, providing pathways for true nanomanufacturing at
drastically reduced cost.
[0004] DSA of block copolymer films on lithographically defined
chemically nanopatterned surfaces is an emerging technology that is
well-positioned to revolutionize sub 10 nm lithography and the
manufacture of integrated circuits and magnetic storage media. See,
for example, Nealey, et al., US Patent Application Publication Nos.
2013/0189504 and 2014/0065379 (both of which are incorporated by
reference). Block copolymer materials self-assemble to form densely
packed features with highly uniform dimensions and shapes in
ordered arrays at the scale of 3 to 50 nm. Chemical pre-patterns
are defined using traditional lithographic materials and processes
such as 193 immersion or electron beam lithography at the scale of
20 to 40 nm. By directing the assembly of block copolymer films on
the chemical pre-patterns, the overall resolution of the
lithographic process may be increased by three to four-fold or
more. This technology can be applied to semiconductors, materials
and equipment, and hard drive manufacture. The interest and
exponential growth in research activity and expenditure is driven
in the semiconductor industry by the prospect of manufacturing
future generations of computer chips according to Moore's law
without having to invest billions of dollars in new fabrication
facilities (i.e., based on extreme ultra violet lithography) that
may or may not be able to meet the resolution requirements already
being demonstrated by DSA. For example, IBM developed a chip with 7
nm transistors with a silicon-germanium alloy (SiGe). The design
was produced using extreme ultraviolet lithography (EUV, =13.5 nm).
The chip was faster with higher-capacity and lower power
consumption. This chip was lab-scale and highly expensive. For hard
drives, block copolymer lithography is the only known technology
that is feasible to fabricate nanoimprint masters to manufacture
bit patterned media at the required storage densities (at least
greater than 2 Terabit/inch.sup.2). Currently DSA of
poly(styrene-block-methymethacrylate) (PS-b-PMMA) films on
lithographically defined chemically nanopatterned surfaces is the
primary focus of activity, and the main research objectives revolve
around demonstrations that DSA can meet manufacturing requirements
related to degrees of perfection, processing latitude, and
integration of the technology with existing infrastructure, and
device design for use with DSA patterns.
[0005] Critical research issues must be addressed in order to push
the DSA technology over the tipping point to widespread
implementation in nanomanufacturing. A key roadblock is the
establishment of proven pathways to realize sub 10 nm resolution,
and scaling to 5 nm; the resolution limit of PS-b-PMMA is .about.12
nm. Neither the semiconductor industry nor the hard drive industry
will implement DSA for a single generation of products. Whereas
substantial effort is being expended by many groups to identify
block copolymer systems capable of self-assembling into the sub 10
nm regime, technology gaps exist in fundamental and technological
understanding as to how those materials may be processed and
directed to assemble and continue to meet the constraints of
manufacturing. Moreover, little or no work is aimed at developing
specialized tools and processes that will be applicable at the
ultimate end-of-the-roadmap length scale.
[0006] Directed self-assembly of block copolymers uses physical
and/or chemical pre-patterns to control the orientation and
alignment of block copolymers (e.g., FIG. 1 and FIG. 2). Strongly
segregating block copolymers (high Flory-Huggins parameter (.chi.),
related to the energy of mixing) can produce higher resolution
patterns. The Flory-Huggins parameter also indicates the
incompatibility of copolymers. Because such block copolymers
typically show large differences in surface energy between the
blocks, one block (with lower surface energy) tends to segregate to
the free surface of films and precludes the assembly of the desired
through-film perpendicularly oriented structures during thermal
annealing. The low-surface-energy domain of the block copolymer
tends to wet the top surface and disrupt the perpendicular
orientation of the block copolymers. A topcoat on the block
copolymer can inhibit the disruption of the polymer orientation. In
this case, thermodynamically favorable boundary conditions at the
top surface of the film can be engineered for directed
self-assembly. However, the topcoat material and coating methods
are limited. Solution spin-coating usually dissolves block
copolymers.
[0007] There exists a need to develop alternative sub-10 nm
patterning methods. These methods can be used to develop faster
devices with higher-capacity and lower power consumption. The
methods should be compatible with current manufacturing methods and
avoid expensive investment in new fabrication facilities.
SUMMARY
[0008] Disclosed is a method for the fabrication of polymeric
topcoat via initiated chemical vapor deposition (iCVD) or
photoinitiated chemical vapor deposition (piCVD) in conjunction
with directed self-assembly (DSA) of block copolymers to generate
high resolution patterns. A topcoat deposited by iCVD or piCVD
allows for conformal, ultra-thin, uniform, pinhole-free coatings.
Combining iCVD or piCVD with DSA enables high-resolution nanoscale
patterning.
[0009] In one aspect, the present disclosure relates to a method of
forming a topcoat on a block copolymer film, comprising the steps
of:
[0010] (a) heating or irradiating an initiator, thereby producing a
gaseous free radical initiator;
[0011] (b) contacting the block copolymer film with the gaseous
free radical initiator and a gaseous monomer, thereby forming a
cross-linked topcoat.
[0012] In some embodiments of the methods disclosed herein, the
block copolymer film is formed by a method comprising the steps
of:
[0013] (a) providing a substrate;
[0014] (b) forming a lithographically defined physical or chemical
pattern on the substrate; and
[0015] (c) coating the substrate with a block copolymer.
[0016] In another aspect, provided herein is an article, comprising
a substrate, and a coating on the substrate, wherein the coating
comprises a block copolymer film and a topcoat on the block
copolymer, wherein the topcoat is deposited by iCVD or piCVD.
[0017] In a further aspect, provided herein is a method of forming
an inorganic pattern on an article, comprising the steps of:
[0018] (a) contacting the article with a gaseous inorganic
material;
[0019] (b) contacting the article with a counter reactant;
[0020] (c) optionally repeating cycles comprising steps (a) and
(b);
[0021] (d) removing the topcoat of the article by a first reactive
ion etching; and
[0022] (e) removing the remaining polymer of the article by a
second reactive ion etching.
[0023] In still another aspect, provided herein is a method of
forming a pattern on an article, comprising the steps of:
[0024] (a) coating the article with a resist;
[0025] (b) forming a resist pattern using lithography to form a
mask;
[0026] (c) removing the topcoat of the article by a first reactive
ion etching;
[0027] (d) contacting the masked article with a gaseous inorganic
material;
[0028] (e) contacting the masked article with a counter
reactant;
[0029] (f) optionally repeating cycles comprising steps (d) and
(e);
[0030] (g) removing the remaining polymer of the masked article by
a second reactive ion etching;
[0031] (h) etching the substrate by a third reactive ion etching;
and
[0032] (i) stripping residues from the substrate.
[0033] In another aspect, provided herein are iCVD or piCVD
topcoats with DSA that create high resolution patterns for data
storage, memory circuits, and micro-processors.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 shows a schematic of a process to create a
lithographically defined chemical pattern and for directed
self-assembly of a block copolymer film.
[0035] FIG. 2 shows the process flow for 4.times. density
multiplication directed self-assembly of VSV using chemical
patterns and iCVD p(DVB) topcoat.
[0036] FIG. 3 shows an initiated chemical vapor deposition (iCVD)
process for forming a cross-linked topcoat directly on a block
copolymer (BCP) film. Vapor-phase vinyl monomer and initiator flow
through an array of heated filaments. The initiators are cracked to
form radicals near the heated filaments. The monomers and radicals
adsorb on the cooled free surface of block copolymer film and
partially diffuse into a block copolymer film. Then, a cross-linked
topcoat film grows from the surface of a block copolymer film via
free radical polymerization. Block copolymer and iCVD topcoat are
seen to be interdiffused at the interface.
[0037] FIG. 4A shows a 45.degree.-tilted cross-section SEM image of
self-assembled VSV film between neutral brush and iCVD p(DVB)
topcoat after SIS through the topcoat.
[0038] FIG. 4B shows a 45.degree.-tilted cross-section SEM image of
self-assembled VSV film between neutral brush and iCVD p(DVB)
topcoat after SIS through the topcoat and breakthrough
BCl.sub.3/Cl.sub.2 RIE.
[0039] FIG. 4C shows a 45.degree.-tilted cross-section SEM image of
self-assembled VSV film between neutral brush and iCVD p(DVB)
topcoat after SIS through the topcoat, breakthrough
BCl.sub.3/Cl.sub.2 RIE, and O.sub.2 RIE.
[0040] FIG. 4D shows a 45.degree.-tilted cross-section SEM image
after pattern transfer to Si substrate by SF.sub.6/O.sub.2 RIE.
[0041] FIG. 5 shows a top-down SEM image of alumina line/space
pattern realized by 4.times. density multiplication directed
self-assembly (DSA) (full-pitch: 18.5 nm) from an e-beam pattern
(insert, full-pitch: 74 nm).
[0042] FIG. 6 shows panels depicting (a) a process flow for pattern
transfer and cut-mask application with iCVD topcoat. E-beam
lithography is possible on top of a fully cross-linked iCVD p(DVB)
topcoat after DSA. (b-d) 45.degree.-tilted cross-section and (e-f)
top-down SEM images after (b, e) hydrogen silsesquioxane (HSQ)
patterning, (c, f) SIS and removal of iCVD topcoat and PS domain,
and (d, g) Si etching and strip off residues. Simple periodic DSA
pattern is trimmed into the desired arbitrary pattern shapes.
[0043] FIG. 7 shows the grazing-incidence small angle x-ray
scattering (GISAXS) pattern obtained from a self-assembled
P2VP-b-PS-b-P2VP (VSV) film between the neutral brush and an iCVD
p(DVB) topcoat.
[0044] FIG. 8A shows panels depicting depth profiling of samples
measured by time-of-flight secondary ion mass specrometry after
spin coating of VSV on a neutral brush layer.
[0045] FIG. 8B shows panels depicting depth profiling of samples
measured by time-of-flight secondary ion mass specrometry after
spin coating of VSV on a neutral brush layer followed by iCVD.
[0046] FIG. 8C shows panels depicting depth profiling of samples
measured by time-of-flight secondary ion mass specrometry after
spin coating of VSV on a neutral brush layer followed by iCVD and
thermal annealing.
[0047] FIG. 9 depicts a schematic of sample preparation for
interfacial analysis.
[0048] FIG. 10 depicts a graph of the water contact angles of
grafted and ungrafted interfaces in comparison with VSV and
p(DVB).
[0049] FIG. 11 depicts a graph of angle-resolved XPS depth-profiles
of nitrogen up to .about.7 nm depth penetration from the
surface.
[0050] FIG. 12 shows ATR-FTIR spectra of four films prepared
according to the sample preparation process depicted in FIG. 9.
[0051] FIG. 13 shows ATR-FTIR spectra of four films prepared
according to the sample preparation process depicted in FIG. 9.
[0052] FIG. 14 shows a schematic of sample preparation for
angle-resolved X-ray photoelectron spectroscopy (AR-XPS) and water
contact angle measurement.
[0053] FIG. 15 shows a schematic of sample preparation for
ATR-FTIR.
[0054] FIG. 16 shows top-down SEM images of PS-b-PMMA (top row) and
P2VP-b-PS-b-P2VP (bottom row) with various film thicknesses
self-assembled between neutral random copolymer brushes and iCVD
p(DVB) topcoats. Perpendicular orientation is obtained for both BCP
systems, regardless of film thickness.
[0055] FIG. 17A shows an SEM image of a self-assembled VSV film
between neutral brush and iCVD p(DVB) topcoat after SIS and RIE
with single step (O.sub.2 RIE).
[0056] FIG. 17B shows an SEM image of a self-assembled VSV film
between neutral brush and iCVD p(DVB) topcoat after SIS and RIE
with two steps (breakthrough RIE+O.sub.2 RIE).
DETAILED DESCRIPTION
[0057] Directed self-assembly (DSA) of block copolymers (BCPs) is a
strategy for patterning at sub-lithographic resolution in which
self-assembling BCPs multiply the density of features in comparison
to a lithographically derived template. On chemical patterns
generated from 193 nm immersion (193i) photolithography with 84 nm
pitch, for example, DSA of polystyrene-block-poly(methyl
methacrylate) (PS-b-PMMA) with 28 nm pitch lines and spaces has
been demonstrated with extremely low levels of defects, approaching
those required for semiconductor manufacturing (0.01/cm.sup.2).
Unfortunately, PS-b-PMMA has a resolution limit of approximately 11
nm. Therefore, BCPs with .chi. (Flory-Huggins interaction
parameter) larger than that of PS-b-PMMA were investigated to
achieve sub-10 nm features. However, for most BCPs except for
PS-b-PMMA, the constituent blocks have considerably dissimilar
surface energies, thus precluding facile assembly of perpendicular,
through-film domains.
[0058] Three general approaches have been developed to circumvent
the problem of dissimilar block surface energies: identification or
synthesis of high-.chi. copolymers with blocks that have equal
surface energy, solvent vapor annealing, or the use of topcoat
layers to achieve similar interfacial energies in place of
disparate surface energies. In the case of topcoats, the design
principles of such layers are well understood and recent efforts
aim at developing materials and processes that are compatible with
high-volume manufacturing. Willson et al. report elegant chemistry
that allows for the topcoat to be deposited on organic-soluble BCP
films by spin coating from aqueous base, and then washed away after
DSA (U.S. Pat. No. 9,157,008 B2, 2015). Potential limitations of
this approach include the number of processing steps required and
the inability to use with BCPs with blocks that are incompatible
with or swell in water and high-.chi. BCPs that often contain
highly polar constituents. Such incompatibility can be overcome by
depositing topcoats from the vapor phase (U.S. Pat. No. 9,040,121
B2, 2015). In both cases, the compositions of topcoats have to be
tailored to achieve a non-preferential surface for a specific BCP
system. Herein, the use of initiated chemical vapor deposition
(iCVD) to deposit a universal topcoat from the vapor phase was
investigated. The motivation for pursing an iCVD or a
photoinitiated chemical vapor deposition (piCVD) approach includes
increasing the diversity of BCP materials that can be used for DSA,
and the direct and seamless integration of the ultra-thin topcoat
layers into pattern transfer processes.
[0059] This disclosure describes the fabrication of polymeric
topcoat via iCVD or piCVD in conjunction with directed
self-assembly (DSA) of block copolymers to generate high resolution
patterns. In certain embodiments, the topcoat polymer used in this
disclosure is poly(divinylbenzene) (P(DVB)) and the block
copolymers (BCP) include
poly(2-vinylpyridine)-block-polystyrene-block-poly(2-vinylpyridine)
(P2VP-b-PS-b-P2VP) and poly(styrene-block-methacrylate)
(PS-b-PMMA). In the semiconductor industry, the formation of high
resolution (<10 nm) patterns is crucial to the improvement of
speed, capacity, and power consumption. The DSA with block
copolymers and topcoats is a low-cost process to improve current
expensive photolithography in cost and pattern resolution. Such a
DSA process requires a thin, pinhole-free polymeric topcoat on the
BCP which is critical to achieve the high resolution patterns.
Also, the topcoat should not damage the BCP layer underneath during
the coating process. Moreover, the surface energy should be matched
with the BCP and be scalable for manufacturing. The topcoat by iCVD
or piCVD, initiated chemical vapor-phase depositions, satisfy these
requirements and enables fabrication of multi-scale patterns. Most
importantly, the iCVD or piCVD topcoat works with multiple BCPs
universally enhancing the graft interface between the topcoat and
BCPs.
[0060] The planar and chemical patterns with different surface
energies toward BCP are first formed on a substrate by
electron-beam (e-beam) lithography for control of the alignment of
BCP. Then, the BCP is spun-cast on the chemical patterns. The
topcoat is deposited on the BCP by iCVD, in which monomer and
initiator vapors are introduced into the vacuum chamber and
initiator is decomposed into radicals near hot-filaments, suspended
above the cool BCP substrate, or piCVD, in which monomer and
initiator vapors are introduced into the UV-irradiated chamber. As
the monomer vapor adsorbs on the BCP, the radicals initiate the
polymerization on the surface growing the topcoat on the BCP. The
following thermal annealing induces the aligned and perpendicular
structures of the BCP. In practice, for replication of the
patterns, converting one domain of the BCP to a metal oxide with an
organometallic precursor increases the etching selectivity.
Following with several dry etching processes replicates the BCP
patterns on the substrate.
[0061] The ultra-thin, uniform, and pin-hole free topcoat via
solvent-free iCVD or piCVD does not damage or dissolve the BCP
layer underneath the topcoat, which is of great importance in
successful DSA process. Moreover, the unique and neutral interface
(i.e., grafting) formed only by iCVD or piCVD permits a topcoat
applicable to multiple BCPs while the solution-based topcoats in
the existing publications are customized to specific BCPs. In
addition to the high resolution pattern formation, the inert and
cross-linked iCVD or piCVD topcoat enables the fabrication of the
topcoat patterns through conventional lithography, thereby
producing the multi-scale patterns. The iCVD or piCVD topcoat is
also readily implemented by current manufacturing processes in
industry with no big expense.
[0062] Solution-based topcoats require careful design of chemistry
for both block copolymer and topcoat to enable a spin on/off
process. There can be a solubility issue with block copolymers and
solution-based topcoats. In DSA, careful selections of block
copolymers and boundary conditions in a given system enable
achievement of targeted sizes and features. For block copolymers to
form features smaller than 10 nm, the interfaces at both the bottom
and the top of block copolymer films should be controlled for
desirable morphologies. Most topcoats used with DSA were customized
for a specific block copolymer.
[0063] The topcoat formed by iCVD or piCVD does not have a
solubility issue with block copolymers because the deposition is
solvent-free. A topcoat formed by iCVD or piCVD is stable against
sequential infiltration synthesis (SIS). This allows pattern
transfer because the topcoat does not need to be removed before
SIS. A topcoat formed by iCVD or piCVD allows for precise control
of thickness and properties of the topcoat. A topcoat formed by
iCVD or piCVD is compatible with conventional lithography (e.g.,
photolithography and e-beam lithography). Multi-patterning can be
carried out using an iCVD or piCVD topcoat.
Definitions
[0064] For convenience, certain terms employed in the
specification, examples, and are conjunctively present in some
cases and disjunctively present in other cases. Multiple elements
listed with "and/or" should be construed in the same fashion, i.e.,
"one or more" of the elements so conjoined. Other elements may
optionally be present other than the elements specifically
identified by the "and/or" clause, whether related or unrelated to
those elements specifically identified. Thus, as a non-limiting
example, a reference to "A and/or B", when used in conjunction with
open-ended language such as "comprising" can refer, in one
embodiment, to A only (optionally including elements other than B);
in another embodiment, to B only (optionally including elements
other than A); in yet another embodiment, to both A and B
(optionally including other elements); etc.
[0065] As used herein in the specification and in the claims, "or"
should be understood to have the same meaning as "and/or" as
defined above. For example, when separating items in a list, "or"
or "and/or" shall be interpreted as being inclusive, i.e., the
inclusion of at least one, but also including more than one, of a
number or list of elements, and, optionally, additional unlisted
items. Only terms clearly indicated to the contrary, such as "only
one of" or "exactly one of," or, when used in the claims,
"consisting of" will refer to the inclusion of exactly one element
of a number or list of elements. In general, the term "or" as used
herein shall only be interpreted as indicating exclusive
alternatives (i.e., "one or the other but not both") when preceded
by terms of exclusivity, such as "either," "one of" "only one of"
or "exactly one of." "Consisting essentially of" when used in the
claims, shall have its ordinary meaning as used in the field of
patent law.
[0066] As used herein in the specification and in the claims, the
phrase "at least one," in reference to a list of one or more
elements, should be understood to mean at least one element
selected from any one or more of the elements in the list of
elements, but not necessarily including at least one of each and
every element specifically listed within the list of elements and
not excluding any combinations of elements in the list of elements.
This definition also allows that elements may optionally be present
other than the elements specifically identified within the list of
elements to which the phrase "at least one" refers, whether related
or unrelated to those elements specifically identified. Thus, as a
non-limiting example, "at least one of A and B" (or, equivalently,
"at least one of A or B," or, equivalently "at least one of A
and/or B") can refer, in one embodiment, to at least one,
optionally including more than one, A, with no B present (and
optionally including elements other than B); in another embodiment,
to at least one, optionally including more than one, B, with no A
present (and optionally including elements other than A); in yet
another embodiment, to at least one, optionally including more than
one, A, and at least one, optionally including more than one, B
(and optionally including other elements); etc.
[0067] It should also be understood that, unless clearly indicated
to the contrary, in any methods claimed herein that include more
than one step or act, the order of the steps or acts of the method
is not necessarily limited to the order in which the steps or acts
of the method are recited.
[0068] In the claims, as well as in the specification above, all
transitional phrases such as "comprising," "including," "carrying,"
"having," "containing," "involving," "holding," "composed of," and
the like are to be understood to be open-ended, i.e., to mean
including but not limited to. Only the transitional phrases
"consisting of" and "consisting essentially of" shall be closed or
semi-closed transitional phrases, respectively, as set forth in the
United States Patent Office Manual of Patent Examining Procedures,
Section 2111.03.
[0069] For purposes of this disclosure, the chemical elements are
identified in accordance with the Periodic Table of the Elements,
CAS version, Handbook of Chemistry and Physics, 67th Ed., 1986-87,
inside cover.
[0070] "BCP" as used herein is an abbreviation for block
copolymer.
[0071] "DSA" as used herein is an abbreviation for directed
self-assembly.
[0072] "iCVD" as used herein is an abbreviation for initiated
chemical vapor deposition.
[0073] "piCVD" as used herein is an abbreviation for photoinitiated
chemical vapor deposition.
[0074] "SIS" as used herein is an abbreviation for sequential
infiltration synthesis.
[0075] As used herein, the term "surface" or "surfaces" or
"substrates" can mean any surface of any material, including glass,
plastics, metals, polymers, paper, fabric and the like. It can
include surfaces constructed out of more than one material,
including coated surfaces. Importantly, all surfaces/substrates of
the disclosure can react with the oxidants/catalysts of the
disclosure, resulting in the covalent attachment of the polymer
coating to the surface/substrate.
[0076] The abbreviations Me, Et, Ph, Tf, Nf, Ts, and Ms represent
methyl, ethyl, phenyl, trifluoromethanesulfonyl,
nonafluorobutanesulfonyl, p-toluenesulfonyl and methanesulfonyl,
respectively. A more comprehensive list of the abbreviations
utilized by organic chemists of ordinary skill in the art appears
in the first issue of each volume of the Journal of Organic
Chemistry; this list is typically presented in a table entitled
Standard List of Abbreviations.
[0077] In one aspect, the present disclosure relates to a method of
forming a topcoat on a block copolymer film, comprising the steps
of:
[0078] (a) heating or irradiating an initiator, thereby producing a
gaseous free radical initiator;
[0079] (b) contacting the block copolymer film with the gaseous
free radical initiator and a gaseous monomer, thereby forming a
cross-linked topcoat.
[0080] In certain embodiments of the methods disclosed herein, the
initiator is selected from the group consisting of peroxides, aryl
ketones, and azo compounds.
[0081] In other embodiments of the methods disclosed herein, the
initiator is triethylamine.
[0082] In some embodiments of the methods disclosed herein, heating
an initiator produces a gaseous free radical initiator using
thermal energy. In another embodiment, the initiator is a peroxide
or an azo compound. In certain embodiments, the initiator is an azo
compound selected from the group consisting of
4,4'-Azobis(4-cyanovaleric acid), 4,4'-Azobis(4-cyanovaleric acid),
1,1'-Azobis(cyclohexanecarbonitrile),
2,2'-Azobis(2-methylpropionamidine) dihydrochloride,
2,2'-Azobis(2-methylpropionitrile), and
2,2'-Azobis(2-methylpropionitrile). In one embodiment, the
initiator is 2,2'-Azobis(2-methylpropionitrile). In certain
embodiments, the initiator is a peroxide selected from the group
consisting of tert-butyl hydroperoxide, tert-butyl peracetate,
cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, tert-amyl
peroxide, tert-butyl peroxide, and tert-butyl peroxybenzoate. In
another embodiment, the initiator is tert-butyl peroxide.
[0083] In other embodiments of the methods disclosed herein,
irradiating an initiator (e.g., using UV-light) produces a gaseous
free radical initiator. Examples of photoinitiators include, but
are not limited to, azobisisobutyronitrile (AIBN), H.sub.2O.sub.2
(hydrogen peroxide), ethyl-2,4,6-trimethylbenzoylphenylphosphinate,
2,2'-azobis(2-methylpropane), benzophenone and its derivatives, and
Michler's ketone. In one embodiment, the initiator is an aryl
ketone.
[0084] In certain embodiments of the methods disclosed herein, the
monomer is at least one of an acrylate, a siloxane, a silazane, and
a vinyl compound. In one embodiment, the monomer is a vinyl
compound. In some embodiments, the monomer polymerizes quickly,
e.g., is an acrylate. Example monomers include, but are not limited
to, methyl methacrylate, butyl acrylate, glycidyl methacrylate,
hydroxyl ethyl methacrylate, ethylene glycol diacrylate, acrylates
with perfluoro side chains (e.g.,
1H,1H,6H,6H-perfluorohexyldiacrylate and 1H,1H,2H,2H-perfluorooctyl
acrylate), 2-vinyl pyridine, 4-vinyl pyridine, p-divinylbenzene,
m-divinylbenzene, stylene, trivinlytrimethylcyclotrisiloxane,
tetravinyltetramethylcyclotetrasiloxane,
trivinyltrimethylcyclo-trisilazane, and
tetravinyltetramethylcyclotetrasilazane. In some embodiments, the
monomer is selected from the group consisting of methyl
methacrylate, butyl acrylate, glycidal methacrylate, vinyl
pyridine, divinylbenzene, stylene,
trivinlytrimethylcyclotrisiloxane,
tetravinyltetramethylcyclotetrasiloxane,
trivinyltrimethylcyclo-trisilazane, and
tetravinyltetramethylcyclotetrasilazane. In yet another embodiment,
the monomer is divinylbenzene. In yet another embodiment, the
topcoat is formed by random copolymerization of extremely
hydrophobic monomer 1H,1H,2H,2H-perfluorodecyl acrylate (PFDA) with
hydrophilic hydrogel former, hydroxyethyl methacrylate (HEMA). By
simply changing the vapor-phase ratio of these comonomers, the mole
% PFDA fraction in the film was systematic varied between 0 and
100%, while maintaining a smooth surface morphology. Thus, the
surface energy of the iCVD or piCVD random copolymer is readily
tuned over a wide range as is desired for controlling the
self-assembly of conventionally synthesized block copolymers. In
other embodiments, the topcoat is formed using a polymer selected
from the group consisting of poly (methyl methacrylate) (PMMA),
poly(4-vinylpyridine-co-divinylbenzene), poly-glycidal methacrylate
(PGMA), polystyrene-random-benzocylcobutene (PS-r-BCB),
poly(2-vinylpyridine)-random-benzocylcobutene (P2VP-r-BCB), and
polystyrene-random-poly(2-vinylpyridine)-random-benzocylcobutene
(PS-r-P2VP-r-BCB).
[0085] In other embodiments, the topcoat is formed by initiated
chemical vapor deposition (iCVD) and grafts to the block copolymer
during deposition. In some embodiments, the topcoat is formed by
photoinitiated chemical vapor deposition (piCVD) and grafts to the
block copolymer during deposition. In another embodiment of the
methods disclosed herein, the topcoat formed by iCVD or piCVD
promotes intermolecular entanglements at the interface with the
block copolymer. In still another embodiment of the methods
disclosed herein, the topcoat forms a neutral interface with the
block copolymer. In yet another embodiment, the thickness of the
grafted interface between the topcoat and the block copolymer is
about 1 nm to about 10 nm. In still another embodiment, the
thickness of the grafted interface between the topcoat and the
block copolymer is about 2 nm to about 5 nm. In some embodiments,
the grafted interface is removed by reactive ion etching (e.g.,
breakthrough reactive ion etching).
[0086] In yet another embodiment of the methods disclosed herein,
the topcoat forms an interface displaying equal preference for both
components of a block copolymer. In still another embodiment, the
topcoat forms an interface with nearly equal interfacial energies
instead of different surface energies. In a further embodiment, the
topcoat strongly interacts with both components of a block
copolymer. In other embodiments, the topcoat is not strongly
preferential to either component of a block copolymer. In another
embodiment, the iCVD or piCVD topcoat process traps chains of the
block copolymer at the interface, which generates a nearly
non-preferential interface for the block copolymer system. In yet
another embodiment, the interfaces drive the perpendicular
orientation of lamella. In other embodiments, the interfaces drive
the perpendicular orientation of the cylinders. In still another
embodiment, the iCVD or piCVD topcoat is compatible with different
block copolymers.
[0087] Previous approaches to chemical vapor deposition, not
initiated, methods to form a topcoat varied the interfacial energy
by introducing various chemical substituents into the CVD precursor
material. In other words, a non-preferential topcoat for one
specific block copolymer system can be achieved by the careful
composition control of topcoat materials. In contrast, the
interfacial energy of "initiated CVD" topcoat is controlled by
block copolymer materials graded at the interface during iCVD or
piCVD process. Therefore, the same iCVD topcoat is compatible to
different block copolymers. Alternatively, the same piCVD topcoat
is compatible to different block copolymers.
[0088] In another embodiment of the methods disclosed herein, the
topcoat forms a neutral interface with the block copolymer. In
still another embodiment, fingerprint morphologies are observed
with a range of block copolymers. In some embodiments, the block
copolymer film is annealed between the neutral substrates modified
by random copolymers and iCVD topcoat. In other embodiments, the
block copolymer film is annealed between the neutral substrates
modified by random copolymers and piCVD topcoat. In yet another
embodiment, fingerprint morphologies were formed regardless of the
thickness of the block copolymer film.
[0089] In other embodiments of the methods disclosed herein, the
topcoat is an insoluble polymer. In another embodiment, the topcoat
is a highly cross-linked polymer.
[0090] In some embodiments of the methods disclosed herein, the
topcoat formed by iCVD or piCVD has similar kinetics to the radical
polymerization in a bulk liquid phase.
[0091] In some embodiments of the methods disclosed herein, the
block copolymer film is formed by a method comprising the steps
of:
[0092] (a) providing a substrate;
[0093] (b) forming a lithographically defined physical or chemical
pattern on the substrate;
[0094] (d) coating the substrate with a block copolymer; and
[0095] (e) annealing the block copolymer to the substrate.
[0096] In other embodiments, the substrate is selected from the
group consisting of silicon wafer, glass slide, quartz,
poly(ethylene terephthalate) (PET) roll, MELINEX.RTM.,
polyethylenenaphtalate (PEN) roll, TEONEX.RTM., kapton roll, paper
roll, polydimethylsiloxane roll, nylon, polyester, polyurethane,
polyanhydride, polyorthoester, polyacrylonitrile, polyphenazine,
latex, teflon, dacron, acrylate polymer, chlorinated rubber,
fluoropolymer, polyamide resin, vinyl resin, GORE-TEX.RTM.,
MARLEX.RTM., expanded polytetrafluoroethylene (e-PTFE), low density
polyethylene (LDPE), high density polyethylene (HDPE), polyimide
(PI), and polypropylene (PP). In some embodiments, the substrate is
selected from the group consisting of silicon wafer, glass slide,
quartz, polyurethane, polyacrylonitrile, polyphenazine, teflon,
polyamide resin, GORE-TEX.RTM., MARLEX.RTM., expanded
polytetrafluoroethylene (e-PTFE), and polyimide (PI). In one
embodiment, the substrate is a silicon wafer. In another
embodiment, the substrate is ultra-thin. In yet another embodiment,
the substrate comprises a high resolution nanopattern. In still
another embodiment, the substrate comprises a high resolution
lithographically defined physical or chemical pattern.
[0097] In other embodiments, the BCP substrate is coated with a
polymer capable of undergoing a cross-linking reaction using an
iCVD process. In certain embodiments, the layer of polymer
deposited by iCVD contains monomers capable of undergoing a
cross-linking reaction. In another embodiment, the monomer is
divinylbenzene. In some embodiments, the monomers are styrene and
divinylbenzene. In another embodiment, the effective cross-linking
density is controlled by the ratio of the styrene to divinylbenzene
monomers. This ratio can affect other parameters including the
surface energy, rms surface roughness, chemical stability
(including subsequent processing steps), and mechanical
properties.
[0098] In another embodiment, an iCVD process is used to coat the
substrate with a layer of polymer from about 5 to about 20 nm in
thickness. In still another embodiment, the layer of polymer
deposited by iCVD is uniform. In a further embodiment, the layer of
polymer deposited by iCVD is ultrathin. In another embodiment, the
layer of polymer deposited by iCVD is pinhole-free. Pinholes form
when the roughness of the film exceeds its thickness. In other
embodiments, the layer of polymer deposited by iCVD is about 1 to
about 5 nm in thickness. In some embodiments, a resist pattern
using lithography forms a mask on the layer of polymer deposited by
iCVD.
[0099] In another embodiment, the substrate is exposed to a polymer
capable of undergoing a cross-linking reaction. In some
embodiments, the polymer capable of undergoing a cross-linking
reaction is a styrene or a styrene derivative. In a further
embodiment, the polymer capable of undergoing a cross-linking
reaction is a pre-cross-linked polymer. In yet another embodiment,
the polymer capable of undergoing a cross-linking reaction is a
pre-cross-linked polystyrene. In still another embodiment, the
pre-cross-linked polystyrene is AZ NLD128.
[0100] In certain embodiments, the thickness and uniformity of
thickness of a lithographically defined physical or chemical
pattern is determined by spin coating. In another embodiment, a
lack of uniformity of thickness leads to non-ideal pattern
transfer. In yet another embodiment, small differences in etch
selectivity leads to non-ideal pattern transfer.
[0101] In some embodiments, the physical or chemical pattern formed
by photolithography or electron-beam lithography.
[0102] In another embodiment, the lithographically defined physical
or chemical pattern control the alignment and orientation of the
block copolymer. In yet another embodiment, the lithographically
defined physical or chemical pattern direct self-assembly of the
block copolymer.
[0103] In still another embodiment, the lithographically defined
physical or chemical pattern enable directed self-assembly of the
block copolymer based on a high resolution nanopattern. In a
further embodiment, the lithographically defined physical or
chemical pattern enable directed self-assembly at 10 nm and
below.
[0104] In yet another embodiment, a trim etch process is used to
define the lithographically defined physical or chemical pattern.
In still another embodiment, the trim etch process results in
structure of about 10 nm. The current technologies for the trim
etch process are limited in terms of uniformity of widths and edge
roughness across large areas. As the width of the lithographically
defined physical or chemical pattern narrows (e.g., the feature
size decreases), the definition of a thinner lithographically
defined physical or chemical pattern becomes more difficult.
[0105] In other embodiments, the chemical pattern provides a
template for self-assembly. For example, a physical pattern
comprises a pattern that has topography. In some embodiments the
lithographically defined pattern can be formed by physical and/or
chemical processes. In other embodiments the lithographically
defined pattern can be formed using topographical templates for
graphoepitaxy or combined chemical and topographical templates. For
example, the lithographically defined pattern can be formed using
methods disclosed in one or more of the following: R. A. Segalman
et al., "Graphoepitaxy of Spherical Domain Block Copolymer Films,"
Adv. Mater., 13: 1152 (2001); Seino Y et al., "Contact hole shrink
process using graphoepitaxial directed self-assembly lithography,"
Micro/Nanolith. MEMS MOEMS, 12(3): 033011; Yi, H. et al., "Flexible
Control of Block Copolymer Directed Self-Assembly using Small,
Topographical Templates: Potential Lithography Solution for
Integrated Circuit Contact Hole Patterning," Adv. Mater., 24: 3107
(2012); Williamson, L. D. et al., "Three-Tone Chemical Patterns for
Block Copolymer Directed Self-Assembly," ACS Applied Materials
& Interfaces, 8: 2704 (2016); and Roel Gronheid et al.,
"Implementation of templated DSA for via layer patterning at the 7
nm node," Proc. SPIE 9423, Alternative Lithographic Technologies
VII, 942305 (Mar. 19, 2015).
[0106] In some embodiments, the process to create a
lithographically defined chemical pattern and for directed
self-assembly of a block copolymer film comprises lithography, a
breakthrough etch, an trim etch, a stripping with solvent, spin
coat brush and anneal, removal of excess brush (FIG. 1). In other
embodiments, the process to create a lithographically defined
chemical pattern and for directed self-assembly of a block
copolymer film comprises e-beam patterning, reactive ion etching
and stripping, backfilling with a neutral brush, and spin coating
with a polymer (FIG. 2).
[0107] In another embodiment, the lithographically defined physical
or chemical pattern has a constant L.sub.s (period between the
chemical pattern). In yet another embodiment, the width W of the
lithographically defined chemical pattern is about L.sub.0/2, where
L.sub.0 is the natural period of the block copolymer. In still
another embodiment, the width W of the lithographically defined
physical or chemical pattern is about 1.5*L.sub.0.
[0108] In some embodiments, the block copolymer self-assembles to
minimize free energy. In yet another embodiment, the block
copolymer is a strongly segregating block copolymer. In still
another embodiment, the block copolymer is a high .chi. block
copolymer. In another embodiment, the block copolymer has a large
Flory-Huggins interaction parameter, which is related to the energy
of mixing. In still another embodiment, the block copolymer is a
lamellae-forming block copolymer. In yet another embodiment, the
block copolymer is a cylinder-forming block copolymer.
[0109] In other embodiments, the lithographically defined physical
or chemical pattern allowed for orientation of the BCP domains
through the iCVD or piCVD topcoat.
[0110] The block copolymer can include any number of distinct block
polymers (i.e. diblock copolymers, triblock copolymers, etc.). A
specific example is the diblock copolymer
poly(styrene-block-methacrylate) (PS-b-PMMA). Any type of copolymer
that undergoes microphase separation under appropriate
thermodynamic conditions may be used. This includes block
copolymers that have as components glassy polymers such as PS and
PMMA, which have relatively high glass transition temperatures, as
well as more elastomeric polymers.
[0111] The block copolymer material may include one or more
additional block copolymers. In some embodiments, the material may
be a block copolymer/block copolymer blend. An example of a block
copolymer/block copolymer blend is PS-b-PMMA (50 kg/mol)/PS-b-PMMA
(100 kg/mol).
[0112] In some embodiments, the block copolymer materials have
interaction parameters (.chi.) greater than that of PS-PMMA. The
interaction parameter .chi. is temperature-dependent; accordingly
block copolymer materials having .chi.'s greater than that of
PS-PMMA at the temperature of assembly can be used in certain
embodiments. In some embodiments, block copolymers having sub-10 nm
domains in the bulk used.
[0113] The block copolymer material may also include one or more
homopolymers. In some embodiments, the material may be a block
copolymer/homopolymer blend or a block
copolymer/homopolymer/homopolymer blend, such as a
PS-b-PMMA/PS/PMMA blend.
[0114] The block copolymer material may comprise any swellable
material. Examples of swellable materials include volatile and
non-volatile solvents, plasticizers and supercritical fluids. In
some embodiments, the block copolymer material contains
nanoparticles dispersed throughout the material. The nanoparticles
may be selectively removed.
[0115] In one embodiment, the block copolymer is formed by reacting
dodecanol with
3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl
isocyanate. In another embodiment, the block copolymer is formed by
the copolymerization of styrene with methyl methacrylate, glycidal
methacrylate, hydroxyl ethyl methacrylate, acrylates with perfluoro
side chains (e.g., 1H, 1H,6H,6H-perfluorohexyldiacrylate and 1H,
1H,2H,2H-perfluorooctyl acrylate), dimethylsiloxane, lactic acid,
2-vinyl pyridine, or 4-vinyl pyridine. In certain embodiments, the
block copolymer is poly(styrene-block-dimethylsiloxane)
(PS-b-PDMS), poly(styrene-block-ethylene oxide) (PS-b-PEO),
poly(styrene-block-lactic acid) (PS-b-PLA),
poly(styrene-block-methacrylate) (PS-b-PMMA), polyhedral oligomeric
silsequioxane (POSS)-containing polymers,
polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP), or
poly(2-vinylpyridine)-block-polystyrene-block-poly(2-vinylpyridine)
(P2VP-b-PS-b-P2VP). In other embodiments, the block copolymer is
PS-b-PMMA, P2VP-b-PS-b-P2VP, PS-b-PEO, or PS-PDMS.
[0116] In other embodiments, directed self-assembly is faster and
results in higher quality structures. In another embodiment, the
width of the lithographically defined physical or chemical pattern
(W) is close to the width of a lamella (natural period of the block
copolymer L.sub.o) (W/L.sub.o=0.5). In another embodiment, the
neutral layer is backfilled by a neutral random copolymer brush. In
yet another embodiment, the neutral regions minimize the
interfacial energy between the substrate and the polymer films
overlaying those regions (the neutral chemistry is a function of n
and the preferential guiding stripe chemistry). In still another
embodiment, low degrees of density multiplication, n, where n is an
integer multiple between the period of the lithographically defined
physical or chemical pre-pattern L.sub.s and the natural period of
the block copolymer L.sub.o, is preferred for faster and
defect-free assembly. In a further embodiment, the film thickness
is minimized within practical limits of supporting micro-phase
separation in the film and domains with aspect ratios high enough
for pattern transfer (film thickness t.about.L.sub.o).
[0117] In certain embodiments, the annealing of step (e) is thermal
annealing.
[0118] In another embodiment, the lithographically defined physical
or chemical pattern and the neutral section have different chemical
functionalities. For example, the chemical functionalities can
include cross-linked polymers and grafted polymers.
[0119] In some embodiments, the topcoat is a non-preferential
wetting topcoat.
[0120] In another embodiment, the topcoat induces a perpendicular
ordering of lamellae. In yet another embodiment, the topcoat
induces a perpendicular ordering of cylinders. In other
embodiments, the topcoat on the block copolymer film controls the
orientation during directed self-assembly. In still another
embodiment, the topcoat enables high-resolution block copolymer
assembly.
[0121] In yet another embodiment, forming the topcoat comprises
iCVD or piCVD of the topcoat in a deposition chamber. In another
embodiment, forming the topcoat is solvent-free. In a further
embodiment, forming the topcoat occurs at low temperatures. In
other embodiments, forming the topcoat does not damage or dissolve
the block copolymer layer underneath the topcoat.
[0122] In some embodiments, the topcoat is uniform.
[0123] In still another embodiment, the topcoat is
pinhole-free.
[0124] In a further embodiment, the topcoat is ultra-thin. In some
embodiments, the thickness of the topcoat is less than about 100
nm. In another embodiment, the thickness of the topcoat is less
than about 10 nm. In yet another embodiment, the thickness of the
topcoat is between about 1 nm and about 5 nm.
[0125] In a further embodiment, high resolution features are
patterned on the topcoat. In some embodiments, solvent annealing is
not needed.
[0126] In some embodiments, the present disclosure relates to a
method of forming a topcoat conformally on a non-planar structure,
such as etching holes that connect layers (called vias).
[0127] In other embodiments, the present disclosure relates to a
method of forming a large scale pattern directly on top of the
topcoat for interconnection.
Devices Comprising Compositions of the Disclosure
[0128] In another aspect, provided herein is an article, comprising
a substrate, and a coating on the substrate, wherein the coating
comprises a block copolymer film and a topcoat on the block
copolymer, wherein the topcoat is deposited by iCVD or piCVD.
[0129] In some embodiments of the article, the topcoat is a
non-preferential wetting topcoat.
[0130] In other embodiments of the article, the topcoat induces a
perpendicular ordering of lamellae. In further embodiments of the
article, the topcoat induces a perpendicular ordering of
cylinders.
[0131] In another embodiment of the article, forming the topcoat is
in a deposition chamber.
[0132] In some embodiments, the topcoat is uniform.
[0133] In still another embodiment of the article, the topcoat is
pinhole-free.
[0134] In yet another embodiment of the article, the topcoat is
ultra-thin. In some embodiments, the thickness of the topcoat is
less than about 100 nm. In another embodiment, the thickness of the
topcoat is less than about 10 nm. In yet another embodiment, the
thickness of the topcoat is between about 1 nm and about 5 nm. In a
further embodiment, high resolution features are patterned on the
topcoat. In still another embodiment, sub-10 nm patterns can be
made on the topcoat. In some embodiments, solvent annealing is not
needed.
[0135] In some embodiments, the pattern is transferred to
silicon.
[0136] In a further aspect, provided herein is a method of forming
a pattern on an article, comprising the steps of:
[0137] (a) coating the article with a resist;
[0138] (b) forming a resist pattern using lithography to form a
mask;
[0139] (c) removing the topcoat from the masked article by a first
reactive ion etching;
[0140] (d) removing the remaining polymer of the article by a
second reactive ion etching; and
[0141] (e) etching the substrate by a third reactive ion
etching.
[0142] In some embodiments, the methods of forming a pattern on an
article include SIS.
[0143] In another aspect, provided herein is a method of forming an
inorganic pattern on an article, comprising the steps of:
[0144] (a) contacting the article with a gaseous inorganic
material;
[0145] (b) contacting the article with a counter reactant;
[0146] (c) optionally repeating cycles comprising steps (a) and
(b);
[0147] (d) removing the topcoat of the article by a first reactive
ion etching;
[0148] (e) removing the remaining polymer of the article by a
second reactive ion etching; and
[0149] (f) etching the substrate by a third reactive ion
etching.
[0150] In a further aspect, provided herein is a method of forming
a pattern on an article, comprising the steps of:
[0151] (a) coating the article with a resist;
[0152] (b) forming a resist pattern using lithography to form a
mask;
[0153] (c) removing the topcoat and one domain of the block
copolymer from the masked article by a first reactive ion
etching;
[0154] (d) etching the substrate with a mask by a second reactive
ion etching; and
[0155] (e) stripping residues from the substrate.
[0156] In still another aspect, provided herein is a method of
forming an inorganic pattern on an article, comprising the steps
of:
[0157] (a) coating the article with a resist;
[0158] (b) forming a resist pattern using lithography to form a
mask;
[0159] (c) removing the topcoat of the article by a first reactive
ion etching;
[0160] (d) contacting the masked article with a gaseous inorganic
material;
[0161] (e) contacting the masked article with a counter reactant;
and
[0162] (f) optionally repeating cycles comprising steps (d) and
(e);
[0163] (g) removing the remaining polymer of the masked article by
a second reactive ion etching;
[0164] (h) etching the substrate by a third reactive ion etching;
and
[0165] (i) stripping residues from the substrate.
[0166] In other embodiments, the article is coated with a resist.
In some embodiments, a resist is applied on top of the topcoat. In
another embodiment, a traditional resist is deposited and processed
on top of the topcoat allowing dual scale patterns to be formed. In
still another embodiment, the topcoat is patternable using
photolithography or e-beam lithography. In yet another embodiment,
the grafted, cross-linked iCVD or piCVD topcoat is durable.
[0167] In some embodiments of the methods disclosed herein, the
first reactive ion etching is a reactive ion etching using a gas
mixture comprising chlorine or a reactive ion etching using a gas
mixture comprising oxygen. In another embodiment, the first
reactive ion etching is a reactive ion etching using a gas mixture
comprising oxygen.
[0168] In some embodiments of the methods disclosed herein, a
counter reactant is selected from the group consisting of water,
O.sub.2, O.sub.3, N.sub.2O.sub.4, N.sub.2O, CH.sub.3COOH,
N.sub.2H.sub.4, NH.sub.3, (CH.sub.3)NNH.sub.2, tBuNH.sub.2, and
CH.sub.2CHCH.sub.2NH.sub.2.
[0169] In another embodiment, a pattern can be transferred to the
underlying block copolymer without removal of the topcoat. In some
embodiments, a DSA pattern can be transferred to the underlying
substrate without removal of the topcoat. In still another
embodiment, the topcoat is transparent to sequential infiltration
synthesis (SIS). In certain embodiments, the topcoat does not need
to be stripped off before SIS. In other embodiments, the SIS does
not react with the PS domains. In some embodiments, the polymer
pattern is converted to an inorganic pattern to increase the
etching selectivity. In certain embodiments, the conversion to an
inorganic pattern is by SIS.
[0170] In yet another embodiment, a gaseous inorganic material
diffuses through the topcoat to affect the block copolymer. In some
embodiments, the gaseous inorganic material is selected from the
group consisting of trimethyl aluminum (TMA), yttrium
tris(2,2,6,6-tetramethyl-3,5-heptanedionate) (Y(thd).sub.3),
diethyl zinc (DEZ), titanium tetrachloride (TiCl.sub.4), vanadium
(V) oxytriisopropoxide (VOTP), palladium (II)
hexafluoroacetylacetonate (Pd(hfac).sub.2), copper
bis(2,2,6,6-tetramethyl-3,5-heptanedionate) (Cu(thd).sub.2),
copper(II) hexafluoroacetylacetonate hydrate (Cu(hfac).sub.2), iron
tris(2,2,6,6-tetramethyl-3,5-heptanedionate) (Fe(thd).sub.3),
cobalt tris(2,2,6,6-tetramethyl-3,5-heptanedionate)
(Co(thd).sub.3), bis(2,2,6,6-tetramethyl-3,5-heptanedionato)barium
triglyme adduct (Ba(thd).sub.2.tri), bis(cyclopentadienyl)
ruthenium (Ru(cp).sub.2), disilane (Si.sub.2H.sub.6), tungsten
hexafluoride (WF.sub.6),
bis(N,N'-diisopropylacetamidinato)copper(I) (Cu(DIA)), nickel (II)
acetylacetonate (Ni(acac).sub.2), antimony pentachloride
(SbCl.sub.5), niobium pentachloride (NbCl.sub.5), niobium
pentethoxide (Nb(OEt).sub.5), titanium isopropoxide
(Ti(iOPr).sub.4), tris(tetramethylcyclopentadienyl) cerium (III),
cyclopentadienyl indium (InCp), tris(i-propylcyclopentadienyl)
lanthanum (La(iPrCp).sub.3), bis(cyclopentadienyl) magnesium
(Mg(Cp).sub.2), bis(cyclopentadienyl) nickel (NiCp.sub.2),
(trimethyl)methylcyclopentadienylplatinum (IV) (Pt(MeCp)Me.sub.3),
bis(pentamethylcyclopentadienyl) strontium (Sr(MesCp).sub.2),
tris(cyclopentadienyl) yttrium (YCp.sub.3), bis(cyclopentadienyl)
la dimethylzirconium (ZrCp.sub.2Me.sub.2),
bis(methylcyclopentadienyl)methoxymethyl zirconium (ZrOMe),
tetrakis(dimethylamino) tin (TDMASn), tetrakis(dimethylamino)
zirconium (TDMAZr), tri s(dimethylamino) aluminum (TDMAAl),
iridium(III) acetylacetonate (Ir(acac).sub.3), niobium
pentafluoride (NbF.sub.5), ferrocene (FeCp.sub.2), cyclohexadiene
iron tricarbonyl (FeHD(CO).sub.3), tetrakis(dimethylamino) antimony
(TDMASb), aluminum trichloride (AlCl.sub.3), niobium (V) iodide
(NbI.sub.5), tin (IV) iodide (SnI.sub.4),
tris(tetramethylcyclopentadienyl)gadolinium(III)
(Gd(Me.sub.4Cp).sub.3), bis(pentamethylcyclo-pentadienyl)barium
1,2-dimethoxyethane adduct (Ba(MesCp)-2-DMA), molybdenum
hexafluoride (MoF.sub.6), tris(tert-pentoxy)silanol (TTPSi),
silicon tetrachloride (SiCl.sub.4), lithium tert-butoxide
(Li(tOBu)), trimethyl indium (TMIn), trimethyl gallium (TMGa), and
dimethyl cadmium (TMCd). In one embodiment, the gaseous inorganic
material is trimethyl aluminum.
[0171] In other embodiments, SIS selectively infuses one of the
domains of the BCPs (e.g., the P2VP domains of PS-b-P2VP) with
alumina. In another embodiment, the trimethyl aluminum coordinates
to the nitrogen atoms in the pyridine groups. In yet another
embodiment, the alumina deposited throughout the P2VP domains
exhibit high etch contrast compared to the PS domains during
reactive ion etching. In some embodiments, SIS permits the pattern
transfer of perpendicularly oriented structures of the P2VP domains
to the substrate. In another embodiment, the Al.sub.2O.sub.3
pattern is transferring to the underlying silicon substrate. In
still another embodiment, the process uses a topcoat and thermal
annealing, not solvent annealing. Solvent annealing has
disadvantages including, but not limited to, problems with
reproducibility, application for large area substrates, pattern
perfection, and dewetting of the block copolymer films from
substrates. iCVD and piCVD overcome many of the issues with solvent
annealing. In other embodiments, SIS enhances pattern transfer.
[0172] In some embodiments of the methods disclosed herein, the
second reactive ion etching is a reactive ion etching using a gas
mixture comprising oxygen. In some embodiments of the methods
disclosed herein, the second reactive ion etching removes the
topcoat and the PS domains.
[0173] In a further embodiment, the resist is patternable using
photolithography or e-beam lithography. In another embodiment, the
resist is selected from the group consisting of hydrogen
silsesquioxane, organosilicate, and polymethyl methacrylate. In
some embodiments, the organosilicate is norbornene
ethyltrimethoxysilane (NH 37) or
p-chloromethylphenyltrimethoxy-silane (Sim et al., Chem. Mater.,
2010, 22 (10), pp 3021-3023). In one embodiment, the resist is
hydrogen silsesquioxane.
[0174] In other embodiments, the resist pattern is formed by
photolithography or electron-beam lithography.
[0175] In one embodiment of the methods disclosed herein, the third
reactive ion etching is a reactive ion etching using a gas mixture
comprising fluorine.
[0176] In some embodiments, the stripping is by using a solvent.
For example, when a PMMA resist is used, the stripping is by using
a solvent, including acetone, chlorobenzene, and
N-methyl-2-pyrrolidone (NMP). In certain embodiments, the stripping
is by hydrofluoric acid and piranha treatment.
[0177] In some embodiments, a dual pattern is formed using the
methods disclosed herein. In other embodiments, a multi-pattern is
formed using the methods disclosed herein. In another embodiment,
the multi-pattern is a line-and-cut pattern.
[0178] In another aspect, provided herein are iCVD or piCVD
topcoats with DSA create high resolution patterns for data storage,
memory circuits, and micro-processors.
[0179] In some embodiments, provided herein is a data storage
device comprising a pattern obtained by any one of the methods
disclosed herein.
[0180] In other embodiments, provided herein is a memory circuit
comprising a pattern obtained by any one of the methods disclosed
herein.
[0181] In another embodiment, provided herein is a micro-processor
comprising a pattern obtained by any one of the methods disclosed
herein.
[0182] In certain embodiments, the iCVD or piCVD topcoat process
can be integrated with the current manufacturing processes of the
semiconductor and the data storage industries. In another
embodiment, the iCVD or piCVD topcoat process can be integrated
with other vacuum processes of the semiconductor and the data
storage industries.
[0183] Advantages of the iCVD or piCVD methods disclosed herein
include, but are not limited to, ability to integrate with current
manufacturing processes; scalability to larger wafer sizes (e.g.,
>1 meter wide); uniformity of films over large areas; ultra-thin
films over large areas; real-time thickness monitoring and endpoint
control; economical, high-purity small molecule reactants (e.g.,
commercially available monomers); use various topcoat materials not
available with spin coating; no solubility issues for reactants; no
dissolution of the underlying block copolymer; minimal
environmental impact (e.g., low-energy, solvent-free processing);
no need for a curing step to remove residual solvent; a precise and
controlled environment for pin-hole free film formation; tight
control over topography (e.g., fewer defects and better pattern
transfer); a non-preferential interface allowing for perpendicular
orientation of the block copolymer during DSA; eliminating a
separate step of topcoat removal during fabrication; reproducible
processing in automated reactors at both lab-scale and
commercial-scale; and systematic tuning of film and surface
properties.
[0184] Having now described the present disclosure in detail, the
same will be more clearly understood by reference to the following
examples, which are included herewith for purposes of illustration
only and are not intended to be limiting of the disclosure.
Examples
Example 1. Directed Self-Assembly Preparation
[0185] A. Preparing Block Copolymer (BCP) Films on Chemical
Pattern
[0186] The first four steps depicted in FIG. 2 show a schematic of
a process to create a lithographically defined chemical pattern and
for directed self-assembly of a block copolymer film. The 6-8
nm-thick cross-linkable polystyrene (.times.PS) mat was first
prepared on the Si wafer by spin coating with AZ NLD128 (obtained
from AZ Electronic Materials) and following thermal annealing at
250.degree. C. for 90 min. A 70 nm-thick gl-2000 (Gluonlab) e-beam
resist layer was coated on xPS mat and exposed by JEOL 9300
electron beam lithography system at Center for Nanoscale Materials
in Argonne National Laboratory. The e-beam doses are in the range
of 260-320 .mu.C/cm.sup.2. Line and space (L/S) resist patterns
with a period of 74 nm (4.times.L.sub.0 of VSV) and various widths
were obtained after being developed in n-amyl acetate (ACROS
ORGANICS) for 20 sec. The xPS mat in the exposed area was
selectively removed by O.sub.2 reactive ion etching (Oxford
PlasmLab 100, RF power 100 W, 10 sccm of O.sub.2 flow, 10 mTorr,
for 19 sec). The remaining e-beam resist was removed by the
repeated sonication with warm N-methylpyrrolidone (NMP,
Sigma-Aldrich), leaving behind PS guiding stripe pattern on Si
wafer (pitch 74 nm, width around 28 nm). PS-r-P2VP brush were then
grafted on the surface of Si wafer between the PS stripe by spin
coating of PS-r-P2VP-r-PHEMA solution (synthesized as described
elsewhere (Ji, S. et al., Macromolecules 2008, 41 (23), 9098-9103),
PS:P2VP:PHEMA=60:38:2 (mol %), 1 wt % in toluene), annealing at
250.degree. C. for 20 min, and washing excess brushes with repeated
sonication using warm dimethylformamide (DMF, Sigma-Aldrich) and
toluene (Sigma-Aldrich) mixture (50:50 v/v). On this chemical
template, a
poly(2-vinylpyridine)-b-polystyrene-b-poly(2-vinylpyridine) (VSV)
film was spin coated with AZ PME844 (obtained from AZ Electronic
Materials). Resulting thickness was around 38 nm.
[0187] B. Initiated Chemical Vapor Deposition (iCVD) Topcoat and
Thermal Annealing for Directed Self-Assembly Using a PS-b-P2 VP
System
[0188] During initiated chemical vapor deposition (iCVD) (FIG. 3)
on a block copolymer (BCP) film, vapors of a monomer and an
initiator flowed through into a vacuum chamber. In the chamber, the
modest temperature (.about.250 to 300.degree. C.) of the array of
resistively heated filament wires caused the initiator to
decompose, producing free radicals. However, the monomers were more
stable and remain intact, such that free radical polymerization
ensued from the combination of species arriving at the surface. The
surface was typically held near room temperature by cooling down
the substrate stage in order to promote the adsorption of reactive
species. In some cases, the free radicals created in the vapor
phase reacted directly with the substrate, resulting in an active
site from which grafted polymer chains grew. Because the iCVD
reactants were small molecules capable of being solvated in the BCP
layer, there was a possibility of a diffuse interface between the
BCP and iCVD layers. Potential reactions between the iCVD reactants
and the BCP should also be considered. A highly cross-linked iCVD
topcoat film grows from the top surface of a block copolymer film
via free radical polymeralization. As a result, the iCVD topcoat
traps chains of the block copolymer at the interface, generating a
nearly non-preferential interface for a given block copolymer
system.
[0189] For the iCVD topcoat, divinylbenzene (DVB) was selected as
the monomer for its ability to form robust organic networks of
exceptionally low roughness. The iCVD approach was ideal for
synthesizing thin films of poly(divinylbenzene) (p(DVB)), as the
insoluble nature of p(DVB) was incompatible with solution-based
thin film forming methods. Ultra-thin pinhole free layers are also
challenging to achieve by traditional spin coating due to the
surface tension effects. However, iCVD readily produced continuous
films of nanoscale thickness as a result of low roughness of p(DVB)
combined with the absence of solvents. Such defect-free and
ultra-thin films were desirable because the topcoat layer
eventually was etched for pattern transfer to silicon.
[0190] The iCVD chamber was described in Lau, K. K. S. and Gleason,
K. K., Macromolecules 2006, 39 (10), 3688-3694. The liquid monomer
(Divinylbenzene, DVB, technical grade, 80%, Aldrich) and initiator
(tert-Butyl Peroxide, TBPO, 98% Aldrich) were used without further
purification. The monomer was vaporized in the liquid jar
maintaining at 55.degree. C. and the initiator was kept at room
temperature. Both vapors were introduced through heated mass flow
controllers (MKS Instrument). The labile peroxide bond of the
initiator was thermally broken by a filament array of parallel
nickel-chromium filaments (Goodfellow) at a distance of 3 cm from
the substrate. The filament and the substrate temperatures were
monitored by two thermocouples (Type K, Omega Engineering). The
substrate temperature was adjusted using a chiller/heater (NESLAB).
The mass uptake of the films was measured by a
temperature-controlled quartz microbalance (QPOD, Infincon)
underneath the filament. p(DVB) topcoats were coated on block
copolymer films, and p(DVB) films were simultaneously deposited on
Si wafers in the same batch for monitoring the thicknesses and
further analysis. The deposition conditions were as follows: a
monomer flow rate of 0.8 sccm, an initiator flow rate of 4.2 sccm,
a pressure of 100 mTorr, the filament and substrate temperatures of
250.degree. C. and 30.degree. C., respectively. The deposition time
(.about.75 min for 7 nm thick topcoat) was intentionally slowed
down to control the thickness precisely and reliably with our
homemade iCVD. Variable-angle spectroscopic ellipsometers (M-2000
& alpha-SE, J. A. Woollam) were used to measure film
thicknesses. All thickness measurements were performed at three
65.degree., 70.degree., and 75.degree. incidence angles using
wavelengths from 400 to 1000 nm for M-2000 and from 380 to 900 nm
for alpha-SE. A nonlinear least-squares minimization was used to
fit ellipsometric data of dry films to the Cauchy-Urbach model. The
thickness was obtained upon convergence of the algorithm. Thermal
annealing for directed self-assembly was performed right after iCVD
process inside of the glove box filled with nitrogen (O.sub.2 and
H.sub.2O<0.1 ppm each). Samples were annealed on a hot plate
pre-heated at 250.degree. C. for 8 h, and then cooled down to room
temperature on a cool metal plate.
[0191] C. Pattern Transfer with Sequential Infiltration Synthesis
and Reactive Ion Etching
[0192] A sequential infiltration synthesis (SIS) process
selectively deposited alumina into the polyvinylpyridine (PVP)
domains. Because the SIS precursors, vapors of trimethylaluminium
and water readily diffused through the ultra-thin and inert p(DVB),
the step usually needed to strip the topcoat prior to SIS was
eliminated. The polystyrene (PS) domains of the VSV were also inert
to SIS precursors. Reactive ion etching (RIE) steps removed both
the topcoat, PS domains, and the remaining organic materials in the
PVP domains. Therefore, the remaining Al.sub.2O.sub.3 patterns
provided the high etch resistance required for pattern transfer
into the underlying silicon.
[0193] Scanning electron micrographs (SEM) were obtained to
demonstrate the process steps for pattern transfer. As expected,
FIG. 4A reveals that the featureless iCVD topcoat completely covers
the morphology of the underlying BCP. Abrief BCl.sub.3/Cl.sub.2 RIE
process (FIG. 4B) followed by a subsequent O.sub.2 RIE fully
removes the remaining PS domains and residual organics, resulting
in clear alumina fingerprint patterns (FIG. 4C). The use of a
two-step etching process to remove organic components will be
discussed later. The subsequent SF.sub.6/O.sub.2 RIE successfully
transferred the alumina fingerprint pattern to Si wafer as
displayed in FIG. 4D.
[0194] SIS of Al.sub.2O.sub.3 was performed at atomic layer
deposition system (ARRADIANCE GEMStar-8). Directed assembled VSV
film with iCVD topcoat was loaded in the reactor and chamber was
evacuated. The temperature of the chamber was kept at 95.degree. C.
Trimethylaluminium (TMA) precursor was first introduced by 10
pulses. Each pulse comprises of 100 ms TMA dose and 10 s pause.
Then, TMA was kept in the chamber for 20 min (above atmosphere
pressure) so that TMA can diffuse into the VSV film through
topcoat. Next, a purge with 200 sccm N.sub.2 flow for 5 min and
evacuation of chamber for 1 min removed excess TMA and byproducts.
The H.sub.2O dose was given in the same fashion with TMA. After
SIS, the removal of topcoat and organic components was performed
with Oxford PlasmaLab 100 system. Topcoat was first removed by
pre-breakthrough reactive ion etching (RIE) (RF power 50 W, ICP
power 300 W, Cl.sub.2 20 sccm+BCl.sub.3 10 sccm, 7 mTorr, for 13
sec). The remaining polymers were removed by O.sub.2 RIE (RF 25 W,
O.sub.2 50 sccm, 80 mTorr, for 2 min). The thin Al.sub.2O.sub.3
layer formed by SIS at the neutral brush was then removed by
additional breakthrough RIE (RF power 100 W, ICP power 600 W,
Cl.sub.2 20 sccm, 10 mTorr, for 7 sec). DSA pattern masked by HSQ
pattern was then transferred to Si wafer based on the RIE recipe
(RF power 15 W, ICP power 800 W, O.sub.2 50 sccm+SF.sub.6 33 sccm,
for 60 sec) (Johnston, D. E. et al., Plasma etch transfer of
self-assembled polymer patterns, 2012; pp 83280A-83280A-8).
[0195] For directed self-assembly (DSA) patterning (FIG. 2), VSV
was spun cast onto a chemically pre-patterned substrate. The ratio
of the natural lamella size of the VSV to the periodicity of the
lithographically defined pattern of the substrate is designed to
yield 4.times. reduction in pitch. Next, the iCVD p(DVB) topcoat
was grown directly on top of the VSV, followed by thermal annealing
to achieve DSA. The sequential infiltration synthesis
(SIS)/reactive ion etching (RIE) steps above produced alumina
line/space patterns with half pitch dimension of 9.3 nm (FIG. 5).
This represents the expected increase of a factor of 4 in
pattern-density over e-beam lithography patterns onto which the BCP
was spun cast.
[0196] D. Post-Patterning on the iCVD Topcoat
[0197] The iCVD p(DVB) is mechanically and chemically robust as a
result of its high degree of cross-linking. It is also insoluble.
Thus, conventional lithographic resists can be spun cast directly
on to the topcoat, allowing for additional features to be defined
at a second larger scale. By following the process shown in FIG. 6
(panel a), a hydrogen silsesquioxane (HSQ) pattern, which spells
out "iCVD Topcoat" (FIG. 6, panels e-g) was prepared by e-beam
lithography on top a 30 nm-thick iCVD p(DVB) film. In this case, an
iCVD topcoat thicker than 7 nm is required to effectively protect
the VSV films from solvents of the HSQ solution. As shown in FIG. 6
(panels b and e), HSQ pattern was clearly observed on the
featureless surface of iCVD topcoat. The thicker iCVD topcoat,
however, limits the diffusion of SIS precursors into the VSV films,
meaning the iCVD topcoat must be pre-etched by O.sub.2 RIE prior to
SIS. After the SIS/RIE steps, alumina line/space patterns with
full-pitch of 18.5 nm were developed outside of HSQ pattern (FIG.
6, panels c and f). Finally, the directed self-assembly pattern was
successfully transferred to the designated regions of Si wafer
masked by HSQ pattern (FIG. 6, panels d and g). This second
lithographic process models existing semiconductor manufacturing
processes for FinFET logic and memory circuits in which a cut-mask
is overlaid on grating patterns to fabricate device-oriented
patterns. The defects in FIG. 5 and FIG. 6 are believed to be
mainly ascribed to SIS/RIE processes rather than the DSA behavior
of BCPs because the line collapses were observed after removal of
organic components from a VSV film. Therefore, further optimization
of process conditions should be able to improve the quality of the
patterns.
[0198] For post-patterning on topcoat/VSV sample, thickness of iCVD
p(DVB) topcoat was increased to 30 nm. The process up to thermal
annealing was identical with the one with thin iCVD topcoat
described above. After directed self-assembly, a 50 nm-thick HSQ
film was spun cast with XR-1541 (Dow Corning) on VSV/topcoat.
E-beam pattern was then exposed by JEOL 9300 system with area dose
of 1,400 .mu.C/cm.sup.2 and developed by MF-CD-26 (Dow Chemical) at
50.degree. C. for 2 min. Exposed iCVD topcoat was pre-etched with
O.sub.2 RIE (RF power 20 W, 10 sccm of O.sub.2 flow, 30 mTorr, for
50 sec). After 5 cycles of SIS, thin Al.sub.2O.sub.3 layer at top
surface stemming from SIS at oxidized surface of VSV was first
removed by brief breakthrough RIE (RF power 50 W, ICP power 300 W,
Cl.sub.2 20 sccm+BCl.sub.3 10 sccm, 7 mTorr, for 29 sec).
Subsequent O.sub.2 RIE (RF 25 W, O.sub.2 50 sccm, 80 mTorr, for 2
min) removed PS domains outside of the HSQ pattern. The DSA pattern
masked by the HSQ pattern was then transferred to Si wafer based on
the RIE recipe described above (Johnston). Finally, residues (HSQ
and alumina-containing VSV) were stripped off by HF and piranha
treatment.
Example 2. Grazing-Incidence Small Angle X-Ray Scattering
(GISAXS)
[0199] Grazing-incident small-angle X-ray scattering (GISAXS) (FIG.
7) verifies the perpendicular orientation of the VSV under the iCVD
topcoat. The incidence angle of the x-ray beam, 0.220, exceeded the
critical angle for p(DVB), as required for penetrating the topcoat,
while falling below the critical angle of the silicon substrate.
The in-plane scattering peak at q.sub.y=0.0339.+-.0.0001
.ANG..sup.- corresponded to perpendicularly oriented lamellae
having a spacing of 18.5 nm.
[0200] A 38 nm-thick VSV film was prepared on neutral substrate
modified by random copolymer brush instead of a chemical pattern. A
7 nm-thick iCVD topcoat was deposited on top of a VSV film with
same process described above. The sample was then annealed at
250.degree. C. for 8 hours. The GISAXS experiment was conducted at
the 8-ID-E beamline in the Advanced Photon Source (APS), Argonne
National Laboratory using x-rays with a wavelength of
.lamda.=1.6868 .ANG. and a beam size of .about.100 .mu.m (h) and 20
.mu.m (v). A 2-D PILATUS 1M-F detector was used to capture the
scattering pattern and was situated at 2165 mm from sample. GISAXS
pattern from self-assembled VSV film between neutral brush and 7
nm-thick iCVD p(DVB) topcoat was taken in a vacuum chamber at an
incident angle of 0.220, above the critical angles of polymers and
below the critical angle of the dilicon substrate. The raw
scattering intensity was corrected for solid angle correction,
efficiency correction for medium (e.g., air) attenuation and
detector sensor absorption, polarization correction, flat field
correction for removing artifacts caused by variations in the
pixel-to-pixel sensitivity of the detector by use of the GIXSGUI
package provided by APS, Argonne National Laboratory. In addition,
the q.sub.y linecut was obtained from a linecut across the
reflection beam center.
Example 3. Time-of-Flight Secondary Ion Mass Spectrometry
(ToF-SIMS)
[0201] The ability of iCVD p(DVB) topcoat to induce the desired
perpendicular ordering of lamella was tested using
poly(2-vinylpyridine)-block-polystyrene-block-poly(2-vinylpyridine)
(P2VP-b-PS-b-P2VP, VSV). The VSV was spun cast onto an unpatterned
neutral random copolymer brush layer on the surface of a silicon
wafer. Next, a 7 nm thick p(DVB) layer was deposited and followed
by thermal annealing. The thickness of topcoat allowing reliable
deposition of smooth film (root mean square roughness: 0.4-0.7 nm)
was chosen. Time-of-Flight Secondary Ion Mass Spectrometry
(ToF-SIMS) depth profiles of nitrogen (N), carbon (C), and silicon
(Si) revealed the evolution of perpendicular orientation through
the key process steps. After spin coating of VSV onto a neutral
substrate (FIG. 8A), the periodic and slight fluctuation of N
profile of VSV exhibited some degree of parallel orientation,
particularly near the free interface. The iCVD process enhanced
this parallel orientation (FIG. 8B). The mobility required to
produce this increased ordering could result from the VSV becoming
plasticized by the iCVD vapors and/or the VSV being lightly
annealed by the heated filaments in the iCVD chamber. The
compositional oscillations completely disappeared after the thermal
anneal (FIG. 8C), as expected upon successful conversion to the
desired perpendicular orientation by iCVD p(DVB) topcoat.
[0202] Samples for ToF-SIMS analysis were prepared by the same
procedure with GISAXS sampling. Depth profiling experiments were
performed using a TOF-SIMS mass spectrometer (TOFSIMS.V, IonTOF
GmbH, Munster, Germany) located at the Materials Research and
Technology department of the Luxembourg Institute of Science and
Technology (LIST, Belvaux, Luxembourg). This instrument is equipped
with a Liquid Metal Ion Gun (LMIG) which delivers a pulsed ion beam
of bismuth clusters. All the experiments presented were carried out
with Bi3 with a kinetic energy of 25 keV. The secondary ions
emitted by the sample surface were accelerated into a
reflectron-type Time-Of-Flight mass analyzer. A cesium beam (Cs+, 3
kV) was used to sputter the sample over a crater size of 250
microns. Spectra were collected from a 50.times.50 .mu.m.sup.2 area
in the center this crater. A low energy (.about.20 eV) electron
flood gun was used to compensate for the local charge
accumulation.
Example 4. Interfacial Analysis on VSV and iCVD p(DVB) Topcoat
[0203] To further understand the observed neutral behavior of the
iCVD p(DVB) as a result of forming a diffuse interface with VSV,
two methods for creating bilayers were compared (FIG. 9): 1) VSV
was spun cast onto an iCVD layer and will be termed "ungrafted",
and 2) the iCVD film was grown on top of the VSV and will be termed
"grafted". Both types of bilayers were exposed to the mixture of
toluene and dimethylformamide (50:50, v/v), which is a good solvent
for VSV, followed by contact angle measurements with water (FIG.
10). For the ungrafted interface, the contact angle (79.3.degree.)
is comparable to that of a single layer p(DVB) (79.8.degree.) used
as a control. This similar hydrophobicity suggests that most or all
of the VSV dissolved away from the ungrafted interface. However,
the contact angle after washing of the grafted bilayer was
significantly higher (83.5.degree.) and indeed close to that of a
single layer VSV control (84.90). The clear difference indicates
that not all of the VSV was removed from the grafted bilayer,
consistent with the hypothesis of a diffuse interface where the
p(DVB) is entangled and/or grafted with VSV.
[0204] Angle-resolved X-ray photoelectron spectroscopy (AR-XPS)
(FIG. 11) detected nitrogen at the grafted interface (.box-solid.),
confirming that pyridine from the VSV (.tangle-solidup.) has
remained behind. No nitrogen was detected by ARXPS from the
ungrafted interface (o). Attenuated Total Reflectance Fourier
Transform Infrared spectroscopy (ATR-FTIR) also clearly revealed
pyridine moieties (.cndot.) only at the grafted interface (FIG.
12). Evidence of chemical reaction of VSV as a result of the iCVD
process is confirmed by the appearance of polysubstituted pyridine
stretches (.diamond-solid.) from the grafted interface along with
their absence from the ungrafted control. The low wavenumber region
(FIG. 13) probes for the existence of the polysubstituted pyridines
and/or benzenes of PS. The C--H deformation vibration of
disubstituted pyridine and/or benzenes (*) were observed only in
grafted interface.
[0205] A. Sample Preparation for AR-XPS and Contact Angle
Measurement
[0206] The roughness of the films is critical for angle-resolved
X-ray photoelectron spectroscopy (AR-XPS) and water contact angle
measurement. For the perfect flatness, the "Grafted" sample was
prepared as described (Inoue, T., et al., Advanced Materials
Interfaces 2015, 2 (10), 1500133) and in FIG. 14. In brief, liquid
glue (Benzophenone composite) was applied on the p(DVB) topcoat. In
order to make strong coupling between glass and glue, a silane
layer was coated on the glass. Then the glue was cured through the
glass by UV-irradiation applying the pressure. After dipping sample
into chlorobenzene for 12 hours, VSV film was dissolved so that a
glass substrate with p(DVB) topcoat can be separated from Si wafer.
Then, a glass substrate with p(DVB) topcoat was washed with
repeated sonication using warm mixture of dimethylformamide and
toluene (v/v=50:50) to completely remove residual VSV.
[0207] B. AR-XPS
[0208] The XPS spectra were obtained using a SSX-100 X-probe
(Surface Science Instruments) spectrometer equipped with a
monochromatized Al K .alpha. source, operated at 1486.8 eV. Survey
scans were conducted, at take-off angles of 0.degree., 15.degree.,
30.degree., 40.degree., 50.degree., 60.degree. and 70.degree. with
the surface normal, to sample the surface at different penetration
depths. During the XPS analysis, the sample charge was compensated
by a 1 eV electron beam at high neutralization current by means of
a Flood Gun. The pass energy was 150 V for survey scans and 50 V
for high resolution scans. The pressure during analysis was kept
under 2.times.10.sup.-9 Torr. A 1 mm diameter beam was used in the
analysis. CasaXPS software was used to calculate the nitrogen
concentration. Samples were stored under vacuum overnight prior to
analysis.
[0209] C. Contact Angle Measurement
[0210] Water contact angles (WCAs) were measured using a goniometer
equipped with an automated dispenser (Model 500, rame-hart
instrument Co.). The WCA was measured using as liquid distilled
water. Static WCAs were measured multiple times in different
positions from three same samples dropping 3 .mu.L water each.
[0211] D. Sample Preparation for ATR-FTIR
[0212] The `Grafted` p(DVB) film over large area interface for
Attenuated Total Reflectance Fourier Transform Infrared
spectroscopy (ATR-FTIR) analysis was prepared as follows: 1)
Sacrificial layer, (polyacrylic acid, PAA) was spun cast on Si
wafer before forming VSV films. 2) VSV films were formed by
spin-coating and then p(DVB) topcoat was deposited by iCVD. 3)
Dissolving PAA in deionized water allowed the VSV/p(DVB) films to
turn over and then be transferred to new Si. Annealing the films
enhanced the adhesion between the films and Si. 4) To expose the
interface, VSV films were dissolved by a mixture of
dimethylformamide and toluene (v/v=50:50) (FIG. 15). Same washing
process was used for `p(DVB)` control sample and `Ungrafted` p(DVB)
film (FIG. 9).
[0213] E. ATR-FTIR
[0214] ATR-FTIR spectra were obtained using a Nicolet 8700 FTIR
spectrometer coupled to an ATR accessary (VariGATR.TM., HARRICK)
with a germanium crystal using OMNIC 6.2 software (Thermo Electron
Corp.). The mercury cadmium telluride (MCT) detector cooled by
liquid nitrogen was used. The active layer was pressed tightly
against the crystal plate. Carbon dioxide and water vapor were
continuously purged out during the measurements. Each spectrum
represents an average of 256 scans collected in the range 700 to
4000 cm.sup.1 at a resolution of 1 cm.sup.1.
Example 5. Neutrality Test of iCVD p(DVB) Topcoat with PS-b-PMMA
and VSV
[0215] The methyl or tert-butoxy radicals, produced by the
decomposition of the initiator (e.g., tert-butyl peroxide) in the
vapor phase, could activate the carbons in the aromatic rings of
2-vinylpyridine (2VP) and/or polystyrene (PS) domains by
abstracting hydrogen. The resulting surface radical sites were able
to react directly with the divinyl benzene (DVB) monomers.
Furthermore, diffusion of monomer and initiator molecules absorbed
from the vapor into block copolymer (BCP), had the potential to
react at the surface and in the subsurface regions and thus, could
result in strong intermolecular entanglements between BCP and
initiated chemical vapor deposition (iCVD) topcoat. Eventually,
through grafting and/or entanglement, the iCVD topcoat attached to
the BCP, which allowed the composition to represent a nearly
neutral and stable interface. Since the majority of polymer chains
of a BCP film underneath the inter-diffused layer do not attach to
the topcoat, they can become mobile upon thermal annealing,
therefore permitting the formation of perpendicularly oriented
lamellae domains. Because poly(2-vinylpyridine) (P2VP) within this
diffuse interface was the reactive site for sequential infiltration
synthesis (SIS), after SIS, a brief breakthrough aluminum etching
of two-step etching was required to clearly develop the underlying
poly(2-vinylpyridine)-block-polystyrene-block-poly(2-vinylpyridine)
(VSV) patterns. The requirement of two-step etching provided
additional evidence of a grafted P2VP component randomly
distributed within the diffuse interface (see Example 6).
[0216] If the mechanism for achieving the top neutral surface was
grafting of BCP chains, the surface energy of the iCVD layer
relative to the BCP should be unimportant. If this was indeed the
mechanism, it would be a very significant finding as the iCVD
p(DVB) would be an effective topcoat for other BCP compositions,
irrespective of surface energy considerations. Thus, the iCVD
topcoat composition would not need to change when utilizing
different BCPs. It would also be anticipated that the iCVD topcoat
would be compatible with BCPs for which no topcoat with a neutral
wetting behavior has been identified. To verify this hypothesis of
grafted BCP chains, the same iCVD p(DVB) topcoat was applied to two
lamellae-forming BCPs with distinctly different surface energy
characteristics, poly(styrene-block-methyl methacrylate)
(PS-b-PMMA) and VSV In both cases, the BCP films with four
different thicknesses in the range of 1.25 to 2.0 L.sub.0 were
prepared by spin coating on the neutral substrates modified by
random copolymer brushes. After iCVD topcoat formation, thermal
annealing, SIS, and breakthrough RIE process, as shown in SEM
images of FIG. 16, the morphologies of perpendicularly oriented
lamellae were observed from two BCPs regardless of the film
thickness, indicating that the iCVD topcoat is neutral for both BCP
systems. This result is in stark contrast to solution-applied
topcoats, where a careful optimization of surface energy matching
must be carried out for each BCP of interest.
[0217] The PS-r-PMMA and PS-r-P2VP brushes were spin coated on top
Si wafers. The films were then annealed at 250.degree. C. for 20
min under N.sub.2 condition, and excess brush materials were washed
out with solvents. On top of neutral substrates, PS-b-PMMA
(37k-b-37k, Polymer Source Inc., L.sub.0.about.40 nm) and
P2VP-b-PS-b-P2VP (12k-b-23k-b-12k, Polymer Source Inc.,
L.sub.0.about.21 nm) were spin coated to be 1.25, 1.5, 1.75, and
2.0 L.sub.0-thick films. After iCVD topcoat, the samples were
annealed at 250.degree. C. for 8 hours under N.sub.2 condition.
Prior to SEM observation, all samples were treated with SIS and
breakthrough RIE as described above.
Example 6. Removal of Topcoat with Single O.sub.2 Reactive Ion
Etching after Sequential Infiltration Synthesis
[0218] After sequential infiltration synthesis (SIS) of alumina
into P2VP domain, the other parts of iCVD p(DVB) topcoat/VSV must
be removed to use the alumina pattern as hard mask for pattern
transfer. If the bilayer is separated with a clear interface,
O.sub.2 reactive ion etching (RIE) should be able to remove topcoat
and PS domain together because p(DVB) itself is an inert component
for SIS. FIG. 17A is a SEM image after 3 cycles of SIS and O.sub.2
RIE (RF power 25 W, O.sub.2 50 sccm, 80 mTorr, for 2 min) on
self-assembled VSV film between neutral brush and iCVD p(DVB)
topcoat. As shown in SEM image, a fingerprint pattern was observed,
but the image was not clear. Moreover, the considerable amount of
residue always remained at the surface even after O.sub.2 RIE with
enough etching time. In order to remove topcoat and PS domain
clearly, breakthrough etching (RF power 50 W, ICP power 300 W,
Cl.sub.2 20 sccm+BCl.sub.3 10 sccm, 7 mTorr, for 13 sec) was
required prior to O.sub.2 RIE (FIG. 17B).
INCORPORATION BY REFERENCE
[0219] All U.S. patents and U.S. and PCT published patent
applications mentioned in the description above are incorporated by
reference herein in their entirety.
EQUIVALENTS
[0220] Having now fully described the present invention in some
detail by way of illustration and example for purposes of clarity
of understanding, it will be obvious to one of ordinary skill clin
the art that the same can be performed by modifying or changing the
invention within a wide and equivalent range of conditions,
formulations and other parameters without affecting the scope of
the invention or any specific embodiment thereof, and that such
modifications or changes are intended to be encompassed within the
scope of the appended claims.
* * * * *